Among the important and time comsuming tasks in surgical procedures is the anastomosis or joining of severed blood vessels, and the success of a surgical procedure may depend on the degree of circulation which is restored through such anastomoses. Conventional anastomosing of blood vessels using sutures is after a tedious procedure, particularly in blood vessels of small diameter, including blood vessels less than one mm. in diameter. Conventional blood vessel suturing techniques are time-consuming, extending the duration of a surgical procedure and successful anastomosing of blood vessels is highly dependent on the proper placement of sutures by the surgeon. Particular difficulty is often encountered in anasotomosing children's vessels which are small and prone to spasm.
Blood vessels of all but the largest size, i.e., the aorta and vena cava in humans, have a naturally occuring contractility, identified as circumferential compressive stress, that resists dilation. These forces become proportionately larger as the vessel diameter decreases and the relative wall thickness increases. Radial tethering forces of tissues do exist around the vessel, but these are of lesser significance than longitudinal vessel motion tethering.
Successful suturing of blood vessels does not assure their continued patency, i.e., their ability to conduct blood flow. Thrombosis (clotting of blood) may act to block blood flow through an anastomosed vessel. In addition to inaccurate placement of sutures, several other factors--spasm, stenosis, and microclamp damage--may be additive in causing thrombosis after microvascular repair. It has been found that continuity of flow during the first twenty minutes after anastomosis is critical in preventing thrombus formation. It has also been found that platelet aggregation, and later resolution occurs in the first several hours after a microvascular anastomosis.
To aid in anastomosing blood vessels, implantable devices which connect severed ends of blood vessels have been described previously, e.g., U.S. Pat. Nos. 3,254,650 and 4,055,186, British Pat. No. 1,181,563, German Fed. Rep. Pat. No. 2,101,282 and Nakayama et al. Surgery December 1962, pp. 918-931. Devices have also been described for everting severed ends of blood vessels to facilitate their suturing, e.g., U.S. Pat. No. 2,180,337.
Our U.S. Pat. No. 4,474,181 describes an external ring to which a pair of vessels having prepared openings may be tethered with sutures so as to hold their intima in fluid-tight apposition. This device provides good assurance or patency by maintaining the lumen of the vessels in an expanded condition at the anastomosis site.
There are advantages to avoiding the use of sutures entirely, particularly for the smaller vessels. In a typical surgical procedure, a large number of small vessels may require anastomosis, and cumulatively the time spent anastomosing these vessels contributes significantly to the time needed to complete the surgical procedure. A. D. Donetskii, Eksperim Khirur. 153-59 (1956) describes an anastomosis ring having outwardly extending protrusions which are used to impale a first vessel end that is inserted through the ring opening and then everted around the outside surface of the ring and a second vessel end which is then draped over the everted vessel end and impaled on the protrusions.
Some of the smaller and weaker vessels tend to tear after the vessel has been impaled on two of the protrusions on an anastomosis ring and the vessel is being stretched to impale on the third of the protrusions. With appropriately proportioned rings having inside surfaces slightly smaller than the unstressed or relaxed exterior diameter of the vessel ends and exterior diameters slightly larger than the relaxed exterior diameter of the vessel, there is seldom a problem in impaling the vessel on the first two of the protrusions, but tearing often occurs when impaling the vessel on the third. If vessel tearing is avoided during the impaling process, a stable, patent anastomosis is generally affected.
It is a general object of the invention to provide a new and improved sutureless anastomosis device in which first and second living vessel ends are impaled on points on an anastomosis ring which has been contracted to a smaller size and which is then shifted to an enlarged size to enlarge the lumens of the vessel ends. More particularly, it is an object to provide such a ring which is contracted in size to miminize tearing of vessel ends during the extension of the vessel ends over the impaling points on the ring.
The invention provides a substantially encircling member in the form of an incomplete ring having an interior surface defining a central opening, an exterior surface, a first ring end and a second ring end and three or more protrusions extending radially outward from the exterior surface for hooking or impaling a pair of prepared ends of living vessels. The incomplete ring is deformable between a first contracted state or configuration and a second expanded state or configuration, and means for maintaining the ring in at least one of said states. With the ring in the first contracted state, a first prepared end of a vessel is drawn through the ring, everted around the end of the ring and along the outside surface where it is impaled on each of the protrusions, in turn. Next, the second end is drawn over the everted and impaled first vessel end and impaled on each of the protrusions, in turn, thereby bringing the intima of the vessels into sealing apposition. With both vessel ends impaled on the ring, the ring is then expanded to its second expanded state, where it is maintained, holding the apposed vessel ends in a slightly stretched state as they heal.
These and other objectives and advantages of the invention will become more apparent from the following detailed description of the invention in reference to the accompanying drawings in which: